- Idle mixture screw out of adjustment. The idle mixture screw controls the amount of fuel added to the air at idle speed. When the engine is cold, the air is denser, and the carburetor needs more fuel to maintain the proper air/fuel mixture. If the idle mixture screw is too far in, the mixture will be too lean, and the engine will stall when the choke is opened.
- Automatic choke is not opening properly. The automatic choke is a device that increases the amount of fuel supplied to the engine when it is cold. When the engine heats up, the choke opens up, reducing the amount of fuel. If the choke is not opening properly, the engine will receive too much fuel when it is cold and stall when the choke is opened.
- Faulty temperature switch. The temperature switch senses the temperature of the engine and sends a signal to the carburetor to open or close the choke. If the temperature switch is faulty, the carburetor will not receive the proper signal, and the choke will not open or close at the correct time.
- Vacuum leak. A vacuum leak can cause the carburetor to receive too much or too little fuel. When the engine is cold, a vacuum leak can cause the carburetor to receive too much fuel, resulting in a rich mixture and stalling.
- Weak Fuel Pump. A weak or faulty fuel pump may not be able to deliver enough fuel to the carburetor, resulting in a lack of idle when cold.
